Senior Staff Software Engineer, Browser – New Products

Mozilla

. Design and implement experiments within browser engine subsystems .

Posted 10/9/2026full-timeRemote • CanadaSenior💰 CA$149,000 - CA$220,000 per yearWebsite

Core Competencies

Role fit

Core Competencies

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Demonstrates deep hands-on expertise in browser engine subsystems, particularly in performance debugging and web platform behavior. Proficient in C++ or Rust, with a strong ability to prototype and evaluate browser capabilities while collaborating effectively within a technical team.

Highest-signal resume keywords

C++ ProficiencyRust ProficiencyBrowser Engine Subsystem ExpertisePerformance DebuggingWeb Platform Behavior Understanding

ATS Keywords

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Applicant Tracking System Keywords

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Hard Skills

Performance MeasurementMemory OwnershipConcurrencyObject LifetimesJavaScript Tool DevelopmentProfilingTracingRegression TestingConformance TestingPrototype Development

Soft Skills

Curiosity About AI AgentsProblem-SolvingCollaboration

Tools & Technologies

AI ToolsDebugging ToolsScripting Tools

Industry Keywords

DOMWeb APIsLayout and RenderingAccessibilityJavaScript RuntimesNetworkingProcess ArchitectureGeckoServoBlink

Tech Stack

Tools & technologies

JavaScriptRustC++

About the role

Key responsibilities & impact

Design and implement experiments within browser engine subsystems
Investigate how internal data structures and execution behavior affect performance, correctness, and developer-tool interfaces
Evaluate approaches for representing and exposing browser state efficiently and accurately
Prototype engine capabilities supporting reliable programmatic interaction with web content
Investigate how document structure, layout, navigation, and event handling affect correctness and performance
Instrument browser behavior and evaluate changes against repeatable tasks
Measure performance and correctness, isolate the effects of changes, and document unsuccessful and successful experiments
Validate that gains hold beyond prototype-development workloads
Profile overhead introduced by new capabilities and pursue measurement-backed improvements
Use AI tools to accelerate coding and analysis, verifying output through debugging, tests, and measurement
Work closely with the team’s technical lead as a hands-on individual contributor

Requirements

What you’ll need

Deep hands-on expertise in at least one browser engine subsystem, such as DOM and Web APIs, layout and rendering, accessibility, JavaScript runtimes, or networking and process architecture
Strong proficiency in C++ or Rust
Experience navigating a large systems codebase
Practical knowledge of memory ownership, concurrency, object lifetimes, and performance debugging
Ability to build JavaScript and scripting tools to exercise and measure work
Ability to investigate unfamiliar code, form precise hypotheses, construct useful prototypes, and interpret results
Strong understanding of web platform behavior and compatibility
Experience with profiling, tracing, regression tests, or conformance tests
Curiosity about AI agents and willingness to work directly with agent harnesses and coding tools
Contributions to Gecko, Servo, Blink, WebKit, or another browser engine are nice to have
Experience maintaining an open-source project is nice to have
Technical leadership in a small team building a new product is nice to have
Experience with accessibility infrastructure, browser security, profiling, or automated evaluation of agent workflows is nice to have

Benefits

Comp & perks

Generous performance-based bonus plans for all eligible employees
Rich medical, dental, and vision coverage
Generous retirement contributions with 100% immediate vesting
Quarterly all-company wellness days
Country-specific holidays plus a birthday day off
One-time home office stipend
Annual professional development budget
Quarterly well-being stipend
Considerable paid parental leave
Employee referral bonus program
Other benefits including life/AD&D, disability, and EAP, varying by country